This invention is related to the field of digital signal processing, and more particularly to the processing of imperfect program specific information for use in the acquisition and decoding of packetized video, audio and other information.
In video broadcast and processing applications, digital video data is typically encoded to conform to the requirements of a known standard. One such widely adopted standard is the MPEG2 (Moving Pictures Expert Group) image encoding standard, hereinafter referred to as the “MPEG standard”. The MPEG standard is comprised of a system encoding section (ISO/IEC 13818-1, 10 Jun. 1994) and a video encoding section (ISO/IEC 13818-2, 20 Jan. 1995). Data encoded to the MPEG standard is in the form of a packetized datastream which typically includes the data content of many program channels (e.g. content corresponding to cable television channels 1-125). Further, several digital services and channels may occupy the frequency spectrum previously occupied by a single analog channel. A 6 MHz bandwidth previously allocated to an analog NTSC compatible broadcast channel may now be split into a number of digital sub-channels offering a variety of services. For example, the broadcast spectrum for RF channel 13 may be allocated to sub-channels including a main program channel, a financial service channel offering stock quotes, a sports news service channel and a shopping and interactive channel. In addition, data conveyed in different sub-channels may be in different data formats (e.g. analog, digital etc.).
In such a digital video system, the processing of ancillary program specific information used in acquiring and decoding packetized data for display on a TV, for example, presents a number of problems. The ancillary program specific information includes data used in identifying and assembling packets comprising selected programs and also includes program guide and text information associated with the transmitted program data. The ancillary program specific information is derived from different broadcast sources e.g. from each broadcaster such as ABC, CBS, NBC, etc., and collated and transmitted as composite program specific information in a packetized datastream together with the program content data of many program channels (e.g. channels 1-125). As a result of this processing, the ancillary program specific information received by a video decoder following transmission may include errors. These errors may be introduced through the collation process, or through broadcaster misunderstandings and incompatibilities as well as through data corruption caused by the transmission process itself. A system, according to the invention principles, acquires and processes ancillary program specific information to alleviate the problems created by these errors.